This invention relates to an improved container for use in a "batch" type process for treating tobacco to increase its filling capacity. In particularly, the invention relates to a tiered container including at least two baskets which provide a uniformed and directional fluid flow distribution.
As is well known in the art, there are various processes for increasing the filling capacity of tobacco by using a volatile organic compound. In these presently known processes, the tobacco is contacted with a liquid or vapor to impregnate the cell with the compound. Then the impregnated tobacco is heated to a temperature above the boiling point of the compound to vaporize the liquid in the tobacco, thus, causing expansion. Embodiments of this basic procedure are described in U.S. Pat. Nos. 3,524,541 and 3,524,542 which issued on Aug. 18, 1970, and U.S. Pat. No. 3,575,178 which issued on Apr. 20, 1971. U.S. Pat. Nos. 3,524,542 and 3,575,178 disclose processes which have a continuous in-feed, thus, they are identified as "continuous" processes.
Also well known in the art is the process for increasing the filling capacity of tobacco by establishing a bed of tobacco in a hermetically sealed chamber, vaccuumizing the chamber, contacting the tobacco in the chamber with a volatile organic compound to impregnate it, and thereafter passing a hot gas through the bed of tobacco to expand it. This process is described in U.S. Pat. No. 3,753,440 which issued Aug. 21, 1973, and it is identified as a "batch" process due to the non-continuous nature of the process. As disclosed in U.S. Pat. No. 3,753,440, the tobacco is placed in a tub or basket which has a screen upon which the tobacco rests which is spaced from the bottom of the tub. The tub has an inlet below the screen through which an impregnated compound and hot gas are injected, whereby the compound and hot gas will pass up through the bed of tobacco carried on the screen.
It has been found that between 450 to 750 pounds of tobacco must be treated during each of the "batch" process cycles in order for the process to be commercially feasible. With this amount of tobacco being processed, several problems result when utilizing a single bed in the "batch" process. Basically, there is a non-uniformity of vapor and steam distribution producing a longer cycle time due to the thickness of the bed which reduces expansion and causes the tobacco in the lower portion of the bed to collapse due to the weight of the tobacco above. In particular, one of the major problems of the single bed basket is the long period of time required to expose the bed of tobacco to the hot gas during the process. In order for these above described processes to produce a satisfactory result in increased filling capacity, the impregnated tobacco must be quickly subjected to the hot gas to vaporize and drive off the volatile compound. If a long period of time is required to contact the tobacco with the hot gas, expansion is impaired. Furthermore, it has been found that excellent results are obtained if the hot gas initially contacts the top of the tobacco bed and penetrates through the bed rather than from the bottom to the top.